The present invention relates to an image processing system, and more particularly to a game computer system processing a variety of images such as a natural picture together with an animation picture.
In a conventional game computer system, image data are defined by color for each dot. The colors of the image data are managed by a color pallet formed in a memory, the color pallet storing many pallet codes (PLT) corresponding to color data.
In the conventional game computer system, image data are compressed (encoded) to be transmitted, and then the compressed data are extended (decoded) to be displayed. Each piece of image data is composed of the pallet code (PLT) and the number (CRL) thereof, which is called a pallet length. The compression method is called a xe2x80x9crun-lengthxe2x80x9d method.
When a single color mode is employed for each screen, image data may be fixed in length (bits); however, when plural color modes are used for one screen, the lengths of the image data are different depending on the color mode.
FIG. 1 shows the formats of image data according to the conventional game computer system, which employs 16, 32, 64 and 128 color modes. The pallet codes are defined by data of 4, 5, 6, and 7 bits for the 16, 32, 64 and 128 color modes, respectively. The length xe2x80x9cLxe2x80x9d of the pallet code in a color mode xe2x80x9cmxe2x80x9d is given by the following equation.
L=log2 m
For example, the length xe2x80x9cLxe2x80x9d of the pallet code in the 128 color mode becomes xe2x80x9c7xe2x80x9d as follows:
L=log2 128=log2 27=7 
The data needs to have a width corresponding to a bus line to be transmitted thereon, because the widths of buses vary depending on the system.
When the image data are transmitted on a 8 bit bus, the data for the 16 color mode may be transmitted in entirely, as shown in FIG. 1; however, when the length of the image data to be transmitted is not a multiple of 8 bits, the data need to be divided, as shown in FIG. 2. For example, image data for the 32 color mode are compressed to 9 bits, the data are divided as 8 and 1 to be transmitted, and as a result, the left over one bit is transmitted with the following data.
In the conventional game computer system, when the screen is divided into plural areas of different colors, the color mode of the greatest number is selected, because each picture is displayed using only one color mode. For example, when an animation picture with 16 colors and a natural picture with 16M colors are synthesized on the screen, the synthesized picture is displayed in the 16M color mode. Such a processing method is not effective for using the memory.
Accordingly, it is an object of the present invention to provide an image processing system in which image data may be scrolled in a horizontal direction even if each color vector factor does not correspond to one dot in a screen.
It is another object of the present invention to provide an image processing system in which image data may be transmitted effectively.
It is still another object of the present invention to provide an image processing system in which image data may be displayed in plural different color modes on a screen effectively.
According to a first feature of the present invention, image data are transmitted with a normal timing when vector factors correspond to dots of the image one for one, and are transmitted with another timing in the other case to scroll the image horizontally.
According to a second feature of the present invention, length of data blocks is adjusted whereby the length becomes an integral multiple of a predetermined fixed value, for example bus width.
According to a third feature of the present invention, a screen is horizontally divided into plural blanking areas. The image data are displayed for each divided blanking area in a predetermined color mode.